Liquid fuel pumping apparatus



May 19, 1970 A. E. .w. AUSTEN 3,513,475

I LIQUID FUEL PUMPING APPARATUS Filed Nov. '5, 1968 INVENTOR 4/, 1444/4144 Md ATTORNEYS United States Patent 3,513,475 LIQUID FUEL PUMPINGAPPARATUS Alan Ewart Walter Austen, Sunbury-on-Thames, England, assignort0 C.A.V. Limited, London, England,

a British company Filed Nov. 5, 1968, Ser. No. 773,497

Claims priority, application Great Britain, Nov. 6, 1967, 50,289/ 67Int. Cl. F04b 1/00, 13/00; F04d 15/00 US. Cl. 417-252 4 Claims ABSTRACTOF THE DISCLOSURE A liquid fuel pumping apparatus including a plungerformed by two cup shaped parts axially slidable one within the other andloaded apart by a coiled compression spring, the plunger being mountedwithin a bore and actuated by a cam the pressure of fuel supplied to thebore acting when it attains a sutficiently high value to effectcompression of the spring so that the effective displacement of theplunger is increased.

This invention relates to liquid fuel pumping apparatus of the kindcomprising in combination, a pumping plunger movable within a bore, acam for imparting movement to the plunger in one direction to pump fuelfrom the bore, the motion of the plunger in the opposite direction beingunder the influence of fuel under pressure entering said bore and actingupon the inner face of the plunger, the pressure of the fuel beingdependent upon the speed at which the apparatus is driven and stop meansfor limiting the extent of movement of the plunger in the otherdirection.

The object of the invention is to provide such an apparatus in a simpleand convenient form.

According to the invention the plunger has associated therewith a partwhich is axially movable relative to the plunger and there is providedspring means for urging the plunger and the part relative to each otherso that said part projects beyond the outer face of the plunger, thearrangement being such that in use, when the fuel pressure is low thestop will be effective upon said part to limit the movement of theplunger in said other direction, and when the fuel pressure is high thespring means will be overcome so that the stop will be effective uponthe plunger to limit the movement thereof.

In the accompanying drawings:

FIG. 1 is a sectional side elevation of one example of a pumpingapparatus in accordance with the invention,

FIG. 2 is a section on the line 22 of FIG. 1, and

FIG. 3 is a view to an enlarged scale of part of the apparatus shown inFIGS. 1 and 2.

In one example of a liquid fuel pumping apparatus in accordance with theinvention, there is provided a body part 1 in which is mounted a rotarycylindrical distributor member 2 which is adapted to be driven in timedrelationship with an engine with which the apparatus is associated. Atone end of the distributor member there is formed a head 3 having atransversely extending bore 4. In the bore 4 is mounted a pair ofreciprocable pumping plungers 9. The space defined between the plungersis in communication with a longitudinal passage formed in the body part1 and which at one point is in communication with a radially disposeddelivery passage 17. The delivery passage is arranged to register inturn and as the distributor member rotates, with a plurality ofequiangularly spaced delivery ports 18 formed in the body part andwhich, in use, are in communication respectively with injection nozzles(not shown) mounted so as to direct fuel into the combustion spaces ofthe associated engine.

For effecting inward movement of the plungers, there is provided in thebody part, an annular cam ring 15 on the internal periphery of which areformed a plurality of pairs of inwardly extending cam lobes seen in FIG.2. Moreover, at their outer ends the plungers bear upon slidablecarriers respectively, each carrier mounted a roller 16 which bears uponthe cam lobes. The outward movement of the carriers is limited by anadjustable stop plate 19 which is mounted upon the distributor member.

Also in communication with the longitudinal passage is a plurality ofinlet passages 11 which are arranged to register in turn and as thedistributor rotates, with an inlet port -12 formed in the body part.

The inlet port 12 is in communication with the outlet 7 of a feed pump5, the rotary part of which is secured to the distributor member. Theinlet 6 of the feed pump is connected to an inlet connection formed inthe body part and the inlet and outlet of the feed pump are incommunication with each other by way of a relief valve 8. The feed pumpis of the vane type and the relief valve as shown, is in the form of asimple spring loaded relief valve. Alternatively it may be in the formof a centrifugally operable relief valve. In each case the outputpressure of the feed pump varies in accordance at the speed at which theapparatus is driven.

For controlling the quantity of fuel which is fed to the space betweenthe pumping plungers, an adjustable throttle 14 is provided intermediatethe inlet port 12 and the outlet 7 of the feed pump. The throttle offersa variable restriction to the flow of fuel and the setting of thethrottle is controlled by a speed sensitive governor (not shown) thecharacteristic of which can be adjusted by the engine operator. In use,fuel enters the space defined between the plungers by way of the inletport 12 and an inlet passage 11 and moves the pumping plungers 9outwardly. Subsequently, inward movement is imparted to the pumpingplungers 'by the action of the cam lobes and fuel is discharged from thespace between the plungers and flows by way of the longitudinal passage10 and the delivery passage 17 to an outlet port 18. If the throttle isset to permit the maximum rate of flow of fuel the extent of outwardmovement of the plungers is limited by the stop plate 19.

In some applications it is desirable that the maximum quantity of fuelwhich can be delivered to an engine at low speeds is smaller than thatwhich can be delivered at high speeds. Such a condition arises when theengine is provided with a turbo supercharger which is relativelyineffective at low speeds. In order to provide for this, one of thepumping plungers 9 and as shown in FIG. 3, is modified by making it oftwo parts, one part 20 is of cup-shaped form and forms the plunger, thebase wall of the cup being directed towards the other plunger. Slidablymounted within the cup-shaped part 20 is a further cup-shaped part 21.Moreover, the base wall of the cup-shaped part 21 is provided with anextension 22 and mounted between the two cup-shaped parts 20, 21 is acoiled compression spring 23 'which acts to urge the part 21 outwardlyfrom the part 20. This movement is resisted by a circlip 24 which islocated within a groove formed in the wall of the part 20. When the partis in contact with the circlip, the extension 22 of the base wallthereof projects slightly beyond the adjacent annular end face of thepart 20.

At low speeds the fuel pressure which is applied to the end face of thepart 20 during the filling stroke is insuf- (ficient to compress thespring 23 with the result that when the rollers move inwardly under theaction of the cam lobes the spring 23 is compressed before actual inwardmovement of the part 20 occurs. At high speeds when the fuel pressure ishigher, the spring 23 is compressed during the filling stroke so thatthe outward movement of the part 20 is slightly larger and the result ofthis is that an increased quantity of fuel is fed to the engine on thenext filling stroke. Since the variation in fuel pressure withincreasing speed is progressive so also is the increase in the quantityof fuel deliv red by the apparatus to the engine.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

-1. Liquid fuel pumping apparatus for supplying fuel to an internalcombustion engine and comprising a body part, a rotary fuel distributormember mounted in said body part and arranged to be driven in timedrelationship with the engine with which the apparatus is asso ciated, afeed pump, the distributor member being provided with a cross bore inwhich is mounted an injection pumping plunger, an annular cam ringhaving cam lobes formed on the internal periphery thereof and which asthe distributor member is rotated effects inward pumping movement ofsaid plunger, said cross bore further being provided with a part whichmovably connects with said plunger by means of a spring means whichurges said part and plunger relative to each other, the part, and springmeans acting to limit the outward movement of said plunger toless thanfull stroke during low pressure pump operation but becoming inactive andallowing a full plunger stroke during high pressure pump operation.

2. A liquid fuel pumping apparatus as claimed in claim 1 in which theplunger and part of the interengaging cupshaped form, with the springmeans in the form of a coiled compression spring acting between theplunger and said part.

3. A liquid fuel pumping apparatus as claimed in claim 2 in which therelative movement of the plunger and part under the action of the springis limited by a circlip retained within a groove formed in the internalperiphery of the plunger.

'4. A liquid fuel pumping apparatus as claimed in claim 3 in which thepart is provided with a projection for contact with said cam ring.

References Cited UNITED STATES PATENTS 2,922,371 1/1960 Bischoif 103161X 3,161,138 12/1964 Koster. 3,166,063 1/1965 Schettler. 3,338,168 8/1967Davis l03-16'6 X 3,392,634- 7/1968 Tobias 106l61 X WILLIAM L. F'REEH,Primary Examiner W. J. 'K-RAUSS, Assistant 'Examiner US. Cl. X.R.

